B2 W2 - Pathophysiology and Clinical Aspects of Asthma (LT) Flashcards
What is the estimated prevalence of asthma in the UK?
10-15% of the population.
What is the hygiene hypothesis?
This theory suggests that extreme cleanliness in childhood increases the likelihood of developing asthma.
Name two environmental factors, aside from hygiene, that contribute to asthma development.
Pollution and occupational sensitizers.
What are the two main classifications of asthma?
-
Extrinsic (“atopic”) asthma
and - Intrinsic asthma.
What is the typical onset age for extrinsic asthma?
Childhood.
What is the typical onset age for intrinsic asthma?
Middle age.
What are the three key features of asthma pathophysiology?
- Reversible airway obstruction
- Airway hyper-responsiveness
- Airway inflammation.
List four key features visible in a histological cross-section of a bronchiole from a patient with severe asthma.
- Mucus plugging
- Inflammatory cells infliltration (especially mast cells, eosinophils, and macrophages)
- Hypertrophy (and hyperplasia) of smooth muscle
- An increased number of goblet cells in the epithelium.
Which cell releases histamine in a process known as ‘degranulation’?
Mast cells.
Which antibody class is responsible for binding allergens and causing degranulation of mast cells?
IgE.
Which T lymphocyte type is most important in the response to allergens in asthma?
- T-helper cells type 2 (Tн2).
- A subtype specifically implicated in allergic responses
What happens during the immediate/early phase of asthma pathogenesis?
The allergen is recognised and bound by IgE antibodies, which then bind to and activate mast cells and cause them to degranulate.
What is the timeframe for the immediate/early phase of asthma pathogenesis?
0-60 minutes after allergen exposure.
What happens during the late phase of asthma pathogenesis?
Chemical mediators (released by the mast cells and TH2 cells) cause
- vascular leakage and oedema
- Infiltration of eosinophils and neutrophils
- Mucus secretion.
What is the timeframe for the late phase of asthma pathogenesis?
1-8 hours after allergen exposure.
What happens during the chronic remodelling phase of asthma pathogenesis?
Structural changes in the airways, often referred to as airway remodelling inluding:
- Smooth muscle hypertrophy and hyperplasia
- Epithelial damage
- Basement membrane thickening.
What is the timeframe for the chronic remodelling phase of asthma pathogenesis?
Months to years after the initial allergen exposure.
List four classic symptoms of asthma.
- Cough
- Wheeze
- Chest tightness
- Dyspnoea (Shortness of breath)
Why is asthma difficult to diagnose in young children?
Diagnostic tests like peak flow or spirometry testing are difficult to perform on young children.
List four signs of asthma exacerbation a doctor may find on examination.
- Difficulty completing full sentences
- High respiratory rate (tachypnoea)
- High heart rate (tachycardia)
- Wheeze
Why might reduced breath sounds indicate a more severe asthma exacerbation?
They suggest very little air is moving in and out of the lungs, possibly due to airway blockage by mucus.
Apart from patient history and response to treatment, list some investigations that can be used to help diagnose asthma.
- Reversibility on spirometry
- Diurnal variation on peak flow monitoring
- Fractional exhaled nitric oxide (FeNO)
- Blood eosinophils.